how to show again the dot in the faces?
Disable Texture Solid option

When that option is enabled, it's supposed that the artist is more intrested in seeing textures than faces dots, so they are automatically hidden (as if you were in texture paint mode) to avoid confusion.

Imagine these dots upon a pois-pattern texture!



As stated by Sergey Sharybin in this task:


  [...] it's currently intentional behavior. Textured shading wouldn't have dots, solid shading with textured solid enabled also wouldn't have dots. This makes sense since this dots wouldn't be much helpful -- they either could obscure texture or the wouldn't be well enough visible.